The invention relates to a vibration damper between two components of a portable handheld work apparatus such as a motor-driven chain saw, a cutoff machine, a blower or the like. The vibration damper is especially mounted between a housing holding an internal combustion engine and a handle for guiding the work apparatus with the handle being attached to the housing.
U.S. Pat. No. 5,368,107 discloses an arrangement of a vibration damper between the housing of a motor-driven chain saw and the handle thereof. The vibration damper comprises a coil spring and each end of the coil spring can be fixed by means of attachment dome which is radially expandable. For this purpose, the attachment dome is expanded by screwing in a threaded attachment fastener. In assembly, it cannot be avoided that the attachment dome rotates with the threaded fastener in the rotational direction. In this way, a torsion force is introduced into the coil spring which cannot be normally reduced so that the vibration damper can have different effects depending upon the assembly.
British Patent 1,170,313 discloses an arrangement of barrel-shaped coil springs between an engine housing and a handle. The barrel-shaped tapered coil springs are each to be fixed by attachment screws arranged in the direction of the longitudinal axis of the screws. This arrangement also cannot be assembled without torsion forces building up so that the vibration-dampening characteristics can be affected disadvantageously.
It is an object of the invention to provide a vibration damper which is so improved that it can be mounted any number of times between components to be damped and each time be free of torsion.
The vibration damper assembly of the invention is disposed between first and second components of a portable handheld work apparatus wherein the first component is a handle for use by an operator for guiding the work apparatus and the second component is a housing accommodating a motor generating vibrations. The vibration damper assembly includes: a coil spring defining a longitudinal center axis and having first and second ends; a first mount provided on the first component for holding the coil spring at the first end thereof; a second mount provided on the second component for holding the coil spring on the second end thereof; the first and second mounts lying approximately on the longitudinal axis and being spaced at a distance from each other; means for facilitating mounting the coil spring between the first and second mounts from one of the first and second ends of the coil spring; and, one of the mounts corresponding to the one end of the coil spring and the one end including means for holding the one end of the coil spring form-tight so as to prevent a rotational movement of the coil spring in the peripheral direction thereof.
The assembly of the coil spring from only one of its ends between the components ensures a simple assembly. Rotational forces which possibly act on the coil spring during the assembly are reduced because the second end is not yet fixed. The first end of the coil spring is mounted from this second end. In the assembly at the second end, the coil spring is form-tight secured against a rotational movement acting in the peripheral direction so that occurring rotational forces are absorbed via the form-tight connection. Stated otherwise, the coil spring remains free of torsion.
The coil spring is free of torsion forces because of the configuration of the vibration damper of the invention so that vibration dampers, which are mounted and configured in the same manner, have the same vibration damping characteristics which are determined exclusively by the material characteristics of the selected coil spring.
According to a further embodiment of the invention, the first end of the coil spring is screwed through the second component in order to assemble this first end. The components themselves can be so aligned in the desired assembly position and can be connected to each other so as to be vibration dampened by a simple mounting of the coil spring from one of its ends. In this way, advantages are afforded in the manufacture as well as in the maintenance of the work apparatus provided with the vibration damper of the invention.
Advantageously, the attachment element is configured as an attachment module having several assembly elements coacting with each other. The attachment module advantageously comprises a connecting element which grabs the end of the coil spring in a form-tight manner and this connecting element is held and secured so that it cannot rotate in a receptacle of the component with which the end of the coil spring is to be connected. Here, it can be advantageous to permit the coil spring to engage form-tightly into the attachment element with an end segment which is bent over radially and especially into that allocated component on which the coil spring is to be fixed.